Add custom tokens for semi-reserved names and variables

[mattacosta]

The following "names" should technically be keywords:

• Constants
  • false
  • true
• Pseudo-types
  • parent
  • self
• Types
  • bool
  • float
  • int
  • iterable
  • null
  • object
  • string
  • void

The following "variables" should technically be keywords:

• $this